Herpes simplex virus (HSV) causes painful lesions on the skin or mucous membranes characterized by vesicles filled with a clear fluid. HSV type 1 (HSV-1) commonly infects the mouth, face, and eyes. HSV type 2 commonly infects the genitals and buttocks. But each serotype can cause infection in all these locations. (Stalkup J R et al., Chapter 80, Human Herpesviruses in Dermatology, Bolognia J L et al. eds. 2003, Mosby Edingurgh, United Kingdom).
Primary infection with HSV typically causes mild fever and lesions at the site of infection. Healing occurs in 8-12 days on average, whereupon the virus migrates to nerve ganglia, where it resides in a latent phase. The virus can be activated again by multiple causes, including physical or emotional stress, colds, fever, immune suppression, or no apparent cause. Activation results in secondary outbreaks. For HSV-1, this usually involves cold sores on the vermillion border of the lips. For HSV-2, the secondary outbreak most commonly causes lesions in or around the genitals, including the vulva, vagina, or penis.
Itching, tingling, and a burning sensation usually precede localized erythema of the skin or mucous membranes by a few hours. Vesicles then form on the skin or mucous membranes. After a few days the ulcers dry and become crusted and generally heal in about 10 days.
The outbreaks cause local pain and a mild generalized fever in many cases.
HSV-2 is generally transmitted by sexual contact. HSV-1 is thought to be transmitted by contact with saliva containing the virus. Infection with one or both serotypes of HSV is extremely common. Some have estimated that 90% of the world's population have antibodies to HSV-1. Forty to sixty million persons in the U.S. are infected with HSV-2. (Stalkup J R et al., Supra.)
There is no cure for HSV infection. Antiviral therapy marginally reduces viral shedding and symptoms in secondary outbreaks. Antiviral therapeutics can heal chronic infection in immunocompromised patients. Antiviral therapeutics are also used prophylactically. But antivirals do not cure the infection, and prophylactic antiviral therapy therefore may be needed for a patient's entire life. (Chakrabarty A et al. 2005, Skin Therapy Lett. 10(1):1-4.) Even with prophylactic use of antivirals, outbreaks still typically occur, although at a lower frequency. Commonly used antivirals for HSV include acyclovir and its derivatives, e.g., valacyclovir and famciclovir. They are usually given orally, but can also be administered by i.v. or in a topical cream. Docosanol cream (ABREVA) has also been shown to decrease the duration of outbreaks slightly (Sacks S L et al. 2001, J Am Acad Dermatol. 45(2):222-30).
New substances and methods to treat HSV infection are needed.